This section provides background information related to the present disclosure which is not necessarily prior art. Recently, increasing number of various vehicles embrace a display device that incorporates techniques of projecting information directly into a human's field of vision, i.e., a head-up display device. The display device of this kind helps to improve a driver's visibility of the environment around the vehicle. A virtual image presented by the display device is superposed on the landscape that can be seen ahead of the vehicle through a windshield of the automobile. The head-up display typically has a display unit as a main functional unit dedicated to virtual image display and a reflection member provided in an instrument panel of a vehicle, and light emitted by the display unit is reflected off the windshield or a combiner that protrudes from an upper surface of the instrument panel toward a driver, so that the driver recognizes what is presented within his or her field of vision during driving.
In the conventional head-up display devices mentioned above, it is necessary to indicate a virtual image in a location relatively distant from the driver so as not to increase driver's burden of focusing his or her eyes on both the real image farther from the driver and the virtual image presented during driving, and one or more reflection members have to be provided to ensure that the virtual image is viewed by the driver at a predetermined distance. Accordingly, the head-up display device often has to incorporate expensive reflection members that cause a manufacturing cost of the head-up display device as a whole to increase. In addition, mounting of the display system of the head-up display device has to be done with utmost accuracy.
Due to fuel economy requirements and limited real estate within an instrument panel, the size of the conventional virtual image and its display position on the windshield is limited. This inhibits a system's ability to function as a warning system as the emitted light is often difficult to ascertain during a warning condition. These limitations heretofore have limited the size and options for head-up display devices.